[media] V4L2: WL1273 FM Radio: Replace ioctl with unlocked_ioctl

Use unlocked_ioctl in v4l2_file_operations. The locking is
already in place.

Signed-off-by: Matti J. Aaltonen <matti.j.aaltonen@nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>